Inverter Control Device for Power Storage Current Variation Suppression
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Solution Overview
Problem
Existing driving systems experience an increase in current variation amount of the power storage device due to the disappearance of switching pulses during high modulation degree operations, leading to increased variation in the sixth electrical frequency of the motor.
Innovation Solution
A driving system that includes a motor, an inverter, a power storage device connected via a power line with a capacitor, and a control device that adds dead time to switching pattern commands of the switching elements, setting an allowable modulation factor based on the circuit characteristics of the DC part to control the current variation amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high modulation degree operation is performed, then motor control performance is improved, but switching pulses disappear due to dead time causing increased current variation amount of power storage device
Solution Approach 1:
The patent applies dynamics by making the dead time variable rather than fixed. The control device adjusts the dead time length based on the modulation degree, specifically extending the dead time when the modulation degree is high to prevent switching pulse disappearance. This dynamic adjustment resolves the contradiction by adapting the dead time to operating conditions, maintaining both motor control performance and power storage device current stability.
Solution Approach 2:
The patent changes the parameter of dead time length based on the modulation degree. When the modulation degree exceeds a threshold, the control device increases the dead time parameter to prevent the switching pulse disappearance that causes current variation. This parameter change approach allows the system to maintain high modulation degree operation while suppressing harmful current variations in the power storage device.
2Ease of operation
If dead time is added to switching pattern commands, then switching control is improved, but switching pulses may disappear causing increased sixth electrical frequency variation
Solution Approach 1:
The patent makes the dead time dynamic by adjusting it according to the modulation degree. Rather than using a fixed dead time that causes switching pulse disappearance, the control device extends the dead time selectively under high modulation degree conditions. This dynamic approach improves switching control while preventing the generation of harmful sixth electrical frequency variations.
Solution Approach 2:
The patent applies preliminary anti-action by proactively extending the dead time before switching pulse disappearance occurs. The control device detects when the modulation degree is high and preemptively increases the dead time to prevent the harmful effect of switching pulse disappearance and subsequent sixth electrical frequency variation, rather than reacting after the problem occurs.
Data Source
AI summary
An object is to suppress an increase in current variation amount of a power storage device. A control device sets an allowable modulation factor, based on a circuit characteristic of a DC part that is on a power storage device side of an inverter, such that a current variation amount of the power storage device becomes equal to or smaller than an allowable current variation amount, and sets switching pattern commands of a plurality of switching elements, based on a set allowable modulation factor.